Contributions to Zoology, 76 (4) – 2007

Littoral Pycnogonida from the Socotra Archipelago

Valerio Bartolino1, Franz Krapp2

1.  Dipartimento di Biologia Animale e dell’Uomo, Università di Roma La Sapienza, Viale dell’Università, 32, I-00185 Roma, Italy,

2.  Zoologisches Forschungsmuseum A. Koenig, Adenauerallee 160, D-53113 Bonn, Germany,

Keywords: monsoon, taxonomy.

Family Phoxichilidiidae Sars, 1891

Genus Anoplodactylus Wilson, 1878

Anoplodactylus erythraeus n. sp.

Material: Shassara, Socotra (12°38’11”N - 54°15’43”E), 31 March 2005, 0-2 m, 1 male (holotype) ZMB 344 comes from macro-algae (i.e. Padina and Dictyota) and sparse hard coral community on small rock boulders. Bartolino leg.

Remarks: This newly found species belongs to a group of closely related Anoplodactylus-species of an extremely attenuated habitus. A fourth species in this complex was described after the submission of the present paper based on the specimens referred by Arango (2003) to A. tenuicorpus. A review of that tenuicorpus-complex is given in Arango and Krapp (2007). Anoplodactylus typhloides is a blind species - from deeper waters - of a roughly similar body shape but otherwise very different from these shallow water species belonging to the tenuicorpus group from coral habitats.

Description: Body extremely slender, segments of about the same diameter as crurigers 2 and 3, separated by nearly 5 times their width. Only few short setae on body surface. Eye cone lowly rounded, placed close to the anterior margin of cephalon, with 4 distinct eyes. Cephalon shortest segment, its crurigers anteriorly bent at an angle of about 60°. Body segments 2 and 3 of subequal length, extremely attenuated, elongated towards their anterior sutures. 4th segment shorter, bent backwards at an angle of about 135°. Abdomen tiny, reaching to about half length of 4th crurigers.

Proboscis long (shorter than either body segments 2 or 3), narrowing at base, with a slight expansion at mid-length and after little narrower stretch follows a subterminal swelling, mouth opening with three distinct lips = the antimere tips.

Chelifore scape extremely slender, longer than proboscis, movable finger distinctly longer than hand. Chela gaping, both finger tips crossing at their extremities, on their ‘cutting’ edge fitted with about 5 needle-like teeth.

Ovigera originating on a swelling ventrally at mid-length of first crurigers, 6-articulated, slightly spinose, 3rd article the longest, its articulation with 4th article forming the most apparent ‘knee’, less so between articles 5 and 6; this terminal article bearing about 7 strong endal setae, which are bent backwards.

Legs extremely slender, coxae 1 and 3 short, coxa 2 around 3 times longer than 3rd one; femur the longest article, tibia 2 almost as long, tibia 1 somewhat shorter (see measurements). All leg articles bearing a few short setae. Cement gland opening slit-like, on the dorsal face of femur of male holotype, slit length almost one sixth of femur length. Tarsus shorter than broad, ventrally bearing one subterminal spine and 3-4 setae. Propodus slender, heel region almost imperceptibly merging into sole, but in this basal region three heavy spines, the third one the longest and with 9 serrations on distal side. Propodal sole bearing about 8 spines which are flanked on both sides by setae, no cutting lamina. Main claw very long, moderately curved, reaching almost to base of serrated spine. Auxiliary claw absent.

Anoplodactylus erythraeus is distinguished from tenui-corpus Child, 1991 by the following characters:

lack of tiny cutting lamina distally on propodal sole;

greater number (about 9 instead of about 5) of spines on sole of propodus;

only one slit-like expanded cement gland opening on dorsal aspect of femur instead of two tiny ones (this seems the most important among those characters);

tibia 2 instead of femur is the longest leg article.

From exaggeratus Stock, 1994 it is distinguished by:

a different palm shape (approaching more the condition in tenuicorpus);

more sole spines (see Table 3);

less crenulations on long sole spine (fig. 4);

the configuration of the very distinct cement gland opening.

From perissoporus Arango et Krapp, 2007 it is distinguished by:

The presence of distinct needle-like teeth on both chela fingers (against none),

the absence of a cutting lamina on the propodal sole,

9 instead of around 13 crenulations on 3rd propodal heel spine,

one prolonged slit-like cement gland opening against 5-9 mounds,

3 distinct (against obliterated) body segment lines.

(See also Table 1 in Arango and Krapp 2007).

Fig. 4. Anoplodactylus erythraeus n. sp. Male (holotype) a) trunk (dorsal view); b) body segment 1; c) proboscis (ventral view); d) chelifore; e) leg 3; f) femur of leg 4; g) distal articles leg 3; h) oviger.

Anoplodactylus turbidus Stock, 1975

Stock 1974: 16 (nomen nudum, without description)

Stock 1975a: 1079-1080; figs. 56b-g

(Red Sea specimens only, fide Child 2002: 1816)

Stock 1975b: 133 (cf. det.)

Child 2002: 1816 (lit.)

Material: Shassara (12°37’40’’N - 54°16’06”E), 8 September 2004, 1-2 m, 1 female with eggs ZMB 366 Bartolino and Mohammed Kaed leg.; Hadibo-Qadheb, 24 September 2004, 1-3 m, 1 female ZMB 365 Bartolino leg. Both from macro-algae and sparse massive hard corals and on rocks, relict reefs and large boulders.

Many small Anoplodactylus-species are ascribed to the Anoplodactylus pygmaeus-complex. It clusters closely similar species whose taxonomic identity is still uncertain. Among all these taxa we can roughly identify two groups on the presence or absence of auxiliary claws. The main species with auxiliaries are: A. minutissimus Stock, 1954, A. micros Bourdillon, 1955, A. trispinosus Stock, 1951 and A. turbidus Stock, 1975. The differences between these species are minute and easier to identify in males than females because their ovigers and the length and position of the cement gland are important identification characters. The toothed finger of chela and the presence of two spines in front of a long lamina on the propodal sole have brought us to the present identification. A certain degree of variability of several diagnostic characters has been previously observed for some species of the A. pygmaeus complex (Stock, 1951; Stock, 1964; Stock, 1975c). The presence of two strong spines on the propodal heel, sometimes reduced to only a single (unpaired) one, is for the first time mentioned for this species, as it was also recorded by Stock (1964) for A. trispinosus.

Several specimens from the Dahlak Archipelago (South Red Sea), previously identified as A. trispinosus, have been assigned to this species together with Ethiopian material after its description by Stock (1975). The same author reported 3 specimens from Madagascar in 1974.

Table 3. Some important characters distinguishing three attenuated Anoplodactylus-species in this complex (for the fourth one see Arango and Krapp, 2007).